1. Field of the Invention
The present invention relates to a semiconductor light emitting device and a method of manufacturing the same, and more particularly, to a nitride semiconductor light emitting device and a method of manufacturing the same, which achieves high resistance to electrostatic discharge (ESD) and high light extraction efficiency.
2. Description of the Related Art
Semiconductor light emitting diodes (LEDs), as one type of semiconductor device, generate light of various colors due to electron-hole recombination occurring at a p-n semiconductor junction when current is supplied. These semiconductor LEDs, greatly advantageous over filament-based light emitting devices, have a long useful life span, low power use, superior initial driving characteristics, high vibration resistance and high tolerance to repetitive power connection/disconnection. This has continually boosted the demand for semiconductor LEDs. Notably of late, much attention has been drawn to group III nitride semiconductors capable of emitting light having a short wavelength such as blue light.
In general, group-III nitride semiconductors (hereinafter, referred to as ‘nitride semiconductors’) have a composition represented by AlxGayIn1-x-yN where 0≦x≦1, 0≦y≦1 and 0≦x+y≦1. The nitride semiconductor light emitting device includes a light emission structure in which an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer are sequentially grown. Light emission occurs as electrons in the n-type nitride semiconductor layer and holes in the p-type nitride semiconductor layers recombine.
The light efficiency of nitride semiconductor light emitting devices is determined by external quantum efficiency and internal quantum efficiency. The internal quantum efficiency of semiconductor light emitting devices reaches approximately 100%, whereas the external quantum efficiency thereof is considerably lower. This is because the total internal reflection of light generated inside semiconductor light emitting devices occurs due to the different refractive indices of the devices and the air when the light strikes the boundaries of the devices. If light generated inside the devices strikes the boundary of the devices at an angle of incidence larger than the critical angle, the light is reflected internally without being extracted to the outside, significantly undermining the light extraction efficiency of the devices.
Also, nitride semiconductor light emitting devices are susceptible to electrostatic discharge (ESD) from people or objects and are easily damaged. The resistance to ESD is one of the requirements for the high reliability of semiconductor light emitting devices, and thus ESD-related characteristics need to be improved.